Package com.google.gwt.user.client.ui

Class FormPanel

  • All Implemented Interfaces:
    HasAttachHandlers, HasHandlers, EventListener, AcceptsOneWidget, FiresFormEvents, HasOneWidget, HasVisibility, HasWidgets, HasWidgets.ForIsWidget, com.google.gwt.user.client.ui.impl.FormPanelImplHost, IsWidget, java.lang.Iterable<Widget>
    public class FormPanel
extends SimplePanel
implements FiresFormEvents, com.google.gwt.user.client.ui.impl.FormPanelImplHost
    A panel that wraps its contents in an HTML <FORM> element.

    This panel can be used to achieve interoperability with servers that accept traditional HTML form encoding. The following widgets (those that implement HasName) will be submitted to the server if they are contained within this panel:

    In particular, FileUpload is only useful when used within a FormPanel, because the browser will only upload files using form submission.

    Example

    public class FormPanelExample implements EntryPoint {

  public void onModuleLoad() {
    // Create a FormPanel and point it at a service.
    final FormPanel form = new FormPanel();
    form.setAction("/myFormHandler");

    // Because we're going to add a FileUpload widget, we'll need to set the
    // form to use the POST method, and multipart MIME encoding.
    form.setEncoding(FormPanel.ENCODING_MULTIPART);
    form.setMethod(FormPanel.METHOD_POST);

    // Create a panel to hold all of the form widgets.
    VerticalPanel panel = new VerticalPanel();
    form.setWidget(panel);

    // Create a TextBox, giving it a name so that it will be submitted.
    final TextBox tb = new TextBox();
    tb.setName("textBoxFormElement");
    panel.add(tb);

    // Create a ListBox, giving it a name and some values to be associated with
    // its options.
    ListBox lb = new ListBox();
    lb.setName("listBoxFormElement");
    lb.addItem("foo", "fooValue");
    lb.addItem("bar", "barValue");
    lb.addItem("baz", "bazValue");
    panel.add(lb);

    // Create a FileUpload widget.
    FileUpload upload = new FileUpload();
    upload.setName("uploadFormElement");
    panel.add(upload);

    // Add a 'submit' button.
    panel.add(new Button("Submit", new ClickHandler() {
      public void onClick(ClickEvent event) {
        form.submit();
      }
    }));

    // Add an event handler to the form.
    form.addSubmitHandler(new FormPanel.SubmitHandler() {
      public void onSubmit(SubmitEvent event) {
        // This event is fired just before the form is submitted. We can take
        // this opportunity to perform validation.
        if (tb.getText().length() == 0) {
          Window.alert("The text box must not be empty");
          event.cancel();
        }
      }
    });
    form.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
      public void onSubmitComplete(SubmitCompleteEvent event) {
        // When the form submission is successfully completed, this event is
        // fired. Assuming the service returned a response of type text/html,
        // we can get the result text here (see the FormPanel documentation for
        // further explanation).
        Window.alert(event.getResults());
      }
    });

    RootPanel.get().add(form);
  }
}

    • Constructor Detail

      • FormPanel

        public FormPanel()
        Creates a new FormPanel. When created using this constructor, it will be submitted to a hidden <iframe> element, and the results of the submission made available via FormPanel.SubmitCompleteHandler.

        The back-end server is expected to respond with a content-type of 'text/html', meaning that the text returned will be treated as HTML. If any other content-type is specified by the server, then the result HTML sent in the onFormSubmit event will be unpredictable across browsers, and the onSubmitComplete event may not fire at all.

        Tip:
        The initial implementation of FormPanel specified that the server respond with a content-type of 'text/plain'. This has been intentionally changed to specify 'text/html' because 'text/plain' cannot be made to work properly on all browsers.

      • FormPanel

        public FormPanel​(NamedFrame frameTarget)
        Creates a FormPanel that targets a NamedFrame. The target frame is not physically attached to the form, and must therefore still be added to a panel elsewhere.

        When the FormPanel targets an external frame in this way, it will not fire the FormSubmitComplete event.

        Parameters:
        frameTarget - the NamedFrame to be targetted

      • FormPanel

        public FormPanel​(java.lang.String target)
        Creates a new FormPanel. When created using this constructor, it will be submitted either by replacing the current page, or to the named <iframe>.

        When the FormPanel targets an external frame in this way, it will not fire the FormSubmitComplete event.

        Parameters:
        target - the name of the <iframe> to receive the results of the submission, or null to specify that the current page be replaced

      • FormPanel

        protected FormPanel​(Element element)
        This constructor may be used by subclasses to explicitly use an existing element. This element must be a <form> element.

        The specified form element's target attribute will not be set, and the FormSubmitCompleteEvent will not be fired.

        Parameters:
        element - the element to be used

      • FormPanel

        protected FormPanel​(Element element,
                    boolean createIFrame)
        This constructor may be used by subclasses to explicitly use an existing element. This element must be a <form> element.

        If the createIFrame parameter is set to true, then the wrapped form's target attribute will be set to a hidden iframe. If not, the form's target will be left alone, and the FormSubmitComplete event will not be fired.

        Parameters:
        element - the element to be used
        createIFrame - true to create an <iframe> element that will be targeted by this form

    • Method Detail

      • wrap

        public static FormPanel wrap​(Element element)
        Creates a FormPanel that wraps an existing <form> element. This element must already be attached to the document. If the element is removed from the document, you must call RootPanel.detachNow(Widget).

        The specified form element's target attribute will not be set, and the FormSubmitCompleteEvent will not be fired.

        Parameters:
        element - the element to be wrapped

      • wrap

        public static FormPanel wrap​(Element element,
                             boolean createIFrame)
        Creates a FormPanel that wraps an existing <form> element. This element must already be attached to the document. If the element is removed from the document, you must call RootPanel.detachNow(Widget).

        If the createIFrame parameter is set to true, then the wrapped form's target attribute will be set to a hidden iframe. If not, the form's target will be left alone, and the FormSubmitComplete event will not be fired.

        Parameters:
        element - the element to be wrapped
        createIFrame - true to create an <iframe> element that will be targeted by this form

      • getAction

        public java.lang.String getAction()
        Gets the 'action' associated with this form. This is the URL to which it will be submitted.
        Returns:
        the form's action

      • getEncoding

        public java.lang.String getEncoding()
        Gets the encoding used for submitting this form. This should be either ENCODING_MULTIPART or ENCODING_URLENCODED.
        Returns:
        the form's encoding

      • getMethod

        public java.lang.String getMethod()
        Gets the HTTP method used for submitting this form. This should be either METHOD_GET or METHOD_POST.
        Returns:
        the form's method

      • getTarget

        public java.lang.String getTarget()
        Gets the form's 'target'. This is the name of the NamedFrame that will receive the results of submission, or null if none has been specified.
        Returns:
        the form's target.

      • onFormSubmit

        public boolean onFormSubmit()
        Fired when a form is submitted.
        Specified by:
        onFormSubmit in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost
        Returns:
        true if the form is submitted, false if canceled

      • onFrameLoad

        public void onFrameLoad()
        Description copied from interface: com.google.gwt.user.client.ui.impl.FormPanelImplHost
        Called when the target frame is done loading.
        Specified by:
        onFrameLoad in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost

      • reset

        public void reset()
        Resets the form, clearing all fields.

      • setAction

        public void setAction​(java.lang.String url)
        Sets the 'action' associated with this form. This is the URL to which it will be submitted.
        Parameters:
        url - the form's action

      • setAction

        public void setAction​(SafeUri url)
        Sets the 'action' associated with this form. This is the URL to which it will be submitted.
        Parameters:
        url - the form's action

      • setEncoding

        public void setEncoding​(java.lang.String encodingType)
        Sets the encoding used for submitting this form. This should be either ENCODING_MULTIPART or ENCODING_URLENCODED.
        Parameters:
        encodingType - the form's encoding

      • setMethod

        public void setMethod​(java.lang.String method)
        Sets the HTTP method used for submitting this form. This should be either METHOD_GET or METHOD_POST.
        Parameters:
        method - the form's method

      • submit

        public void submit()
        Submits the form.

        The FormPanel must not be detached (i.e. removed from its parent or otherwise disconnected from a RootPanel) until the submission is complete. Otherwise, notification of submission will fail.

      • getSynthesizedIFrame

        Element getSynthesizedIFrame()